1. Field of the Invention
The present invention relates to a pulse phase difference encoding device, an oscillation device and a combination thereof wherein a delay circuit consisting of a plurality of interconnected delay elements is provided to perform the encoding of a phase difference in a pulse signal, the outputting of an oscillation signal according to digital data or both of them concurrently based on delayed signals sequentially output at predetermined connecting points of the delay elements.
2. Related Arts
As pulse phase difference encoding devices for encoding a phase difference in a pulse signal into digital data, pulse phase difference encoding devices such as that disclosed in Japanese unexamined patent publication No. H3-220814 are known wherein a delay circuit consisting of a plurality of interconnected delay elements is provided; the first pulse signal is input to the delay element at the first stage of the delay circuit; the delay element in the delay circuit at which the input pulse has arrived at the point in time at which the next pulse is input is detected; the number of the delay elements connected up to this element from that at the first stage is encoded to obtain digital data corresponding to the phase difference between those pulse signals.
Further, as oscillation devices whose oscillation frequencies can be digitally controlled over wide ranges from several hundred KHz to several tens MHz, digitally controlled oscillation devices such as that disclosed in Japanese unexamined patent publication No. H5-102801 have been proposed, wherein a delay circuit consisting of a plurality of interconnected delay elements is provided as in the pulse phase difference encoding devices as described above and wherein the delaying operation of the delay circuit is started by inputting a pulse signal to the delay element at the first stage of the delay circuit and, thereafter, an oscillation signal is output in a cycle according to digital data by repeating the execution of operations such as outputting an oscillation signal when pulse signals are output from the delay elements at connecting positions corresponding to digital data in the delay circuit and initializing the delay circuit concurrently.
With those devices, the detection of pulse phase differences and the control over an oscillation frequency can be performed at time resolution which is determined by the delay time of the delay elements of the delay circuits. It is therefore possible to achieve a significant improvement over the conventional devices with respect to the accuracy of the detection of pulse phase differences and the accuracy of the control over an oscillation frequency.
Further, since these devices can accurately perform the detection of pulse phase differences and the control over an oscillation frequency, it is possible to provide a PLL (phase locked loop) for communication apparatuses, motor controlling apparatuses, etc. which can be digitally controlled and which is highly accurate by combining a pulse phase difference encoding device and a digitally controlled oscillation device, for example, as disclosed in Japanese unexamined patent publication No. H5-102801. Alternatively, the ratio of the cycle of an oscillation signal to be measured to that of a reference signal, i.e., the oscillation frequency of the oscillation signal can be detected, for example, in a manner utilizing two pulse phase difference encoding devices simultaneously wherein the cycle of the reference oscillation signal input to one of the pulse phase difference encoding device is encoded; the cycle of the oscillation signal input to the other pulse phase difference encoding device is encoded; and division is carried out on the encoded data to obtain the above-mentioned ratio. Further, it is also possible to use two digitally controlled oscillation devices concurrently and to synthesize the oscillation signals of those oscillation devices to generate an oscillation signal having a frequency higher than the frequencies which can be obtained by those oscillation devices.
Such concurrent use of the devices as described above will provide a successful result if the delay circuits incorporated in those devices operate at completely the same time resolution. However, variations in the time resolution among the delay circuits in those devices caused by variations in the delay elements of the delay circuits will result in variations in time resolution among the oscillation signals of the devices which are in accordance with the encoded data of pulse phase differences and digital data. This has resulted in problems such as that the operation of a PLL can not be digitally controlled with high accuracy if the PLL is constituted by a pulse phase difference encoding device and a digitally controlled oscillation device as described above.
Such a problem can be avoided by sharing a single delay circuit among those devices instead of providing each of those devices with a delay circuit. In conventional devices, however, since a delay circuit is initialized and is activated for a delaying operation when the first pulse signal to be phase-difference-encoded is input from the outside or when an oscillation signal is output, it has not been possible to share a single delay circuit among such devices.